The present invention relates generally to the field of processing Trinidad Lake Asphalt, and, more particularly, to improved methods for processing Trinidad Lake Asphalt which make it more user friendly and which enhance the characteristics thereof when used in road building and other applications.
Trinidad Lake Asphalt (hereafter xe2x80x9cTLAxe2x80x9d), also known as Trinidad Natural Asphalt or Epure, is a naturally occurring Lake Asphalt which is found in the island of Trinidad in the West Indies. This natural phenomenon, TLA, is different from and is not to be confused with tar sands, or tar pits or even asphalt which is a natural or mechanical mixture in which bitumen is associated with mineral matter. An accepted definition which has been given to TLA is: an asphalt which, as found in nature, is in a condition of flow or fluidity. As dug from the earth, TLA contains thirty percent (30%) water which is normally removed through refining under conditions of temperature. The molten material is then filtered and typically packed into silicone treated hardboard drums. The drums are typically silicone treated as the temperature at which the molten TLA is filled into the drum is generally around 163xc2x0 C.
The known processing methods for TLA have several disadvantages. More particularly, TLA is generally dug from the earth and packaged in silicone coated drums. This bulk form of TLA cannot be conveniently used or shipped. Moreover, since the TLA is refined at approximately 163xc2x0 C., the drums must be coated with a releasing agent, such as silicone, that is able to withstand such high temperatures. After the TLA is packed into the hardboard drums, the material contracts or shrinks upon cooling. Thus, the cooled drums generally have to be brought back to the stills to be xe2x80x9ctopped upxe2x80x9d after cooling in order to provide a full drum. The typical drums weigh about 230 kg. The disposal of these drums after use is now an environmental problem.
The drums are generally required for local and export sales of TLA because the TLA has a melting point of approximately 85xc2x0 C. and, as a result, the TLA suffers from the Sol Effect, in that at room temperature TLA behaves like a liquid material even though it is considered a solid material at that temperature. Thus, with known techniques for processing TLA, the TLA must be placed in containers like hardboard drums in order to properly contain the material during shipment and/or storage. Flexible containers, such as plastic bags, cannot be used because of the Sol Effect and resulting deformity of the material when placed in such containers during storage or shipment. Moreover, if the TLA is formed into discrete elements, such as pellets, within a container, the pellets will coalesce during storage or shipment, thereby preventing the TLA from being used or maintained in a pelletized form.
Rubberized bitumens (ex refinery) which are presently being used as road building materials suffer from the fact that they phase separate, and also cannot be used in extreme conditions of high and low temperatures. TLA is known the world over as being capable of enhancing the properties of road mixes. In fact, TLA has been used as a xe2x80x9cmodifierxe2x80x9d in road building and rubber has been added to road mixes to improve the ductility of the binder. This feature (ductility) of the binder has been found to be useful for low temperate regions to avoid cracking of the pavement. Examples of such use are found on George Washington Bridge, New York and JFK Airport. However, in extremely cold conditions even the road mixes which contain TLA as a modifier contract, causing fissures or small cracks. The polymer modified bitumens, which are supposed to alleviate this problem have failed miserably due to phase separation.
In road building, the SHRP specifications specifically outline what performance standard a finished road mix must have in certain places, such as in the United States. TLA has never enjoyed major success in the marketplace, because of the handling problems which are associated with the material, as described in detail above, notwithstanding the fact that TLA has the advantage of being non-carcinogenic and an entirely natural material. TLA has not heretofore been provided in a user friendly state which enables it to be commonly used in applications such as road building, where, for example, adherence to the SHRP specifications is required. Moreover, the used drums which contained the TLA present serious disposal problems for the end user and serious environmental concern in places such as the United States.
Thus, a need exists for an improved method for processing TLA which overcomes the disadvantages of the prior art processing methods.
It is therefore a primary object of the present invention to provide an improved method for processing TLA which results in a more user friendly TLA product.
A further object of the present invention is to provide an improved method of processing TLA which enables the TLA product to be more easily and cost effectively used in applications such as road building.
Another object of the instant invention is to provide an improved method of producing a TLA product which enables said product to be more easily handled, stored and transported.
Yet another object of the instant invention is to provide an improved method of producing a TLA product which enables said product to more easily be used in road building applications requiring adherence to the SHRP specifications and/or other specifications.
A further object of the invention is to provide an improved method of processing TLA which enables said TLA to be stored and transported in a more environmentally friendly manner.
A further object of the instant invention is to provide an improved method of processing TLA which enables said TLA to be cost effectively used, stored and transported in a crushed, pelletized or powdered form without coalescing.
Yet another object of the instant invention is to provide an improved method of processing TLA which prevents the TLA product from suffering from the Sol Effect.
Yet another object of the instant invention is to provide an improved method for processing TLA which uses non-molten mixers (e.g. Banbury, high shear internal mixers, etc.) instead of molten mixers (heaters, etc.) for the purpose of mixing the Trinidad Lake Asphalt and at least one other raw material.
These and other objects and advantages are achieved by the present invention, which provides an improved method of processing Trinidad Lake Asphalt, including the steps of removing Trinidad Lake Asphalt from the earth and adding thereto at least one stabilizing material of a type which increases the melting point of said Trinidad Lake Asphalt to produce a stabilized product. The stabilizing material is preferably clay, carbonaceous material, silica and/or polymer. Molten or non-molten mixers may be used to combine the TLA and stabilizer to produce a stabilized product. The stabilized product is then pulverized or otherwise broken down into discrete elements, such as pellets, powder, crushed or cut elements. The discrete elements may then be packaged into, for example, polyethylene bags and stored or transported for later use. The stabilizer prevents the discrete elements from coalescing during storage or transport. The bags of discrete TLA elements may be used in road building mixes simply by throwing the entire bag, including the bag itself, if desired, into a mixer with the other road building materials.
In accordance with a more particular object of the instant invention, a polymer, such as rubber, may be used as the stabilizer, thereby resulting in a rubberized and optionally pelletized TLA product. If stabilizers other than polymers are used, a non-rubberized and optionally pelletized TLA product can be produced.
In accordance with another aspect of the instant invention, an improved method of processing Trinidad Lake Asphalt is provided which includes the steps of removing TLA from the earth, breaking the TLA down into a plurality of discrete elements, and adding a surface tension modifier to the plurality of discrete elements to make a stabilized TLA product. The surface tension modifier may simply be a coating on the discrete elements which increases the surface tension thereof or it may be such that it reacts with the TLA to increase the surface tension thereof.